Process for the recovery of minor amounts of solvent from solventextracted hydrocarbons



United States Patent O the public This invention relates to a processfor the removal of minor amounts of certain organic contaminants fromliquid hydrocarbons. More particularly, the invention relates to aprocess for removing minor quantities of solvents firom the products ofa solvent extraction process conducted .on certain petroleum stocks.

Solvent extraction processes are widely employed today in the petroleumand chemical industries. In the petroleum industry, solvent extractionis employed, for example, for the production of relatively pure aromatichydrocarbons which may be employed as chemical intermediates or forincreasing the aromatic content of gasoline stocks so as to raise theiroctane number.

The most common source of aromatic-containing stocks in the petroleumindustry is the product of a catalytic reforming operation. Catalyticreforming refers to a process wherein a naphtha cut from crude oilboiling in the range of about ZOO-450 R, and often 225 to 400 F., iscontacted with a platinum-ccntaimng or other catalyst under conditionsof elevated temperature and pressure. The products of this opertion isrich in aromatic hydrocarbons but also contains significant amounts ofparafiinic hydrocarbons.

Various processes have been developed for extracting the valuablearomatic hydrocarbons from the product of a catalytic reformingoperation. One of these processes involves the use of a selectivesolvent which preferentially dissolves the aromatic hydrocarbons. One ofthe drawbacks of such process has been that the hydrocarbons becomecontaminated with minor amounts of the solvent. Accordingly, thisinvention is concerned with the removal of such minor amounts of solventfrom the product of a solvent extraction process. The removal of thesolvent not only enhances the value of the products but it may alsopermit the re-use of the solvent, which offers obvious economicadvantage.

In the solvent extraction of catalytic reformate, the reformate iscontacted in an extraction zone with a selective solvent, resulting inthe yield :of two separate phases. The various solvents for use in thisextraction process are well known in the art. One class of solventsknown to the art which finds particular utility for solvent extractingcatalytic reformate are polar organic solvents. Of this class, hydroxyamines and their derivatives, which selectively dissolve aromatichydrocarbons from paraffinic hydrocarbons, are illustrative. Theseinclude phenylethanolamine, phenyldiethanolarnine, triethalolamine,diethylaminoethanol, dioctylaminoethanol, ethylphenylethanolamine,monoethanolamine, diethanolalmine, monoisopropanolamine,triisopropanolamine, diisopropanolamine, N- morpholinethanol,hydroxvethylethanoldiamine, triethanolamine abietate, triethanolaminenaphthenate, butyl diethanolamine, N-dibutylaminoethanol,p-tertiary-amyl phenyldiethanolamine, p-tertiaryamylphenylmonoethanolamine, diethylamino-2,3 propanediol, etc. Inparticular, phenylethanolamine has been found a very effective selectivesolvent for this extraction process, and the invention will be describedin connection with this solvent.

The extract phase from the extraction operation con- 2 Claims.

3,112,258 Patented Nov. 26., 1963 tains the bulk of the solventemployed. The major amount of this solvent is removed trom the extractby conventional means. For example, the solvent may be separated fromthe extract phase by simple distillation. Regardless of the methodemployed, it is quite diflicult to obtain a complete removal of solventfrom the extract phase, and minor amounts of the selective solventusually remain in the aromatic product. Similarly, small amounts ofsolvent are included in the raflinate phase obtained from the extractionoperation. The amount of solvent remaining in these products will varydepending upon the solvent and process conditions selected for theextraction process, and it may vary widely in the range of 0.01% up toabout 5% by weight of the total hydrocarbon stock.

It is therefore the object of this invention to remove such minoramounts of solvent from the products of a solvent extraction process.The process of this invention is broadly applicable to removing minoramounts of any polar organic solvent for aromatic hydrocarbons remainingin either the extract or raflinate phases but has particular utility inconnection with the solvents selected from that class of hydroxy aminecompounds mentioned above.

Briefly stated, this invention is a process which comprises the step ofcontacting the products of a solvent extraction with a bed of adsorbentmaterial.

The nature of the adsorbent materials is not critical in the process,and any solid particles having adsorbent characteristics may beemployed, such as, for example, various types of commercially availablecharcoals, clays, bone chars, bauxitels, spent catalytic crackingcatalysts, and natural or synthetic zeolites. The particle size of thesolid adsorbent and the size of the bed are not critical and will dependin large part on the volume of the product stream that must be treated.In general, the particle size of the adsorbent may vary between 10 andQ00 mesh. Flow rate of the product stream need only be suflicient toinsure good contact within the adsorption bed, and normally the flowrate may range from space velocities of approximately 1 to 10 volumes ofproduct stream feed per hour per volume of bed.

The process may be conducted at atmospheric temperature and pressure. Itis preferred, however, that the process be conducted at temperatures ofapproximately 60 F. to 220 F. but below 250" F. so as to avoidpolymerization of any olefinic compounds which may be present in theproducts treated. These olefins are not objectionable when the stock isto be used as a gasoline component. The pressure may besuper-atmospheric but there is no advantage to this unless thetemperature is close to or above the boiling point of any component ofthe stock.

A more complete understanding of the invention may be gained from thefollowing working examples, which are offered to illustrate and not tolimit this invention.

Example I 80 bbl. of heptane per hour, containing 0.3 Weight percent ofphenylethanolamine, corresponding to a raffinate phase, was passed overan adsorption bed having a volume of ft. containing 2800 lbs. charcoalhaving a particle size in the range of 10 to 200 mesh. The operation wascarried out at atmospheric pressure and at a temperature of F. Theeffluent contained substantially no phenylethanolamine and the operationwas continued until an analysis of the product showed a phenylethanolamine content exceeding 10 ppm. During this period, 800 bbl. of heptanewas treated.

Example II A hydrocarbon stream comprising a 70% toluene and 30% heptanemixture containing 2 weight percent of (B phenylethanolamine,corresponding to an extract phase, was passed at a rate of 100 bbl./hr.over an adsorption bed having a volume of 75 ft. containing 2800 lbs.charcoal having a particle size in the range of to 200 mesh. Theoperation was carried out at atmospheric pressure and at a temperatureof 130 F. The efiluent contained substantially no phenylethanolamine andthe operation was continued until an analysis of the effluent showed aphenylethanolamine content exceeding 40 p.p.m. During this period, 55bbl. of the hydrocarbon stream was treated.

It is contemplated that when the concentration of the solvent in theproduct exceeds a predetermined amount, the flow of hydrocarbon to thebed is discontinued and the adsorbent particles in the bed may bediscarded and replaced with fresh particles. Alternatively, the spentbed may be regenerated by any suitable means known to the art and theadsorbent re-used. Regeneration of the bed may be accomplished, forexample, by steam stripping. A preferred means of regenerating the spentbed is disclosed in my co-pending application Serial No. 773,155, filedNovember 12, 1958.

Although the process of this invention may be readily adapted to removeany amount of contaminating solvent within the concentration rangestated heretofore as 0.01% to 5% by weight, it may be desirable when theconcentration of the solvent is 2% or above to first water-wash theproducts by methods well described in the prior art to reduce thesolvent content to below approximately 1% before treating the productswith the process of this invention for the substantially completeremoval of solvent.

It will be obvious to those skilled in the art that variousmodifications of the process described herein may be readily madewithout departing from the spirit and intent of this invention, andhence it is desired that application for Letters Patent cover all suchmodifications of the invention as would reasonably fall Within the scopeof the appended claims.

I claim:

1. A process for removing phenylethanolamine from a hydrocarbon liquidstream obtained in the selective solvent extraction of catalyticreformate with phenylethanolamine, said stream containing tfrom about0.001 to about 5% phenylethanolamine, comprising the steps ofintroducing said liquid hydrocarbon stream into a closed vesselcontaining a bed of adsorbent material, contacting said hydrocarbonstream with said bed at a temperature under 250 F., and recovering thehydrocarbon stream substantially free from said phenylethanolamine fromsaid vessel.

2. The process of claim 1 in which the adsorbent material is charcoal.

References Cited in the file of this patent UNITED STATES PATENTS1,882,002 Dietrich Oct. 11, 1932 2,398,101 Lipkin Apr. 9, 1946 2,651,594Blatz Sept. 8, 1953 2,711,433 Pofienberger June 21, 1955 2,744,942Wankat May 8, 1956 2,856,442 Munk Oct. 14, 1958 2,858,902 Cottle Nov. 4,1958 OTHER REFERENCES Nevens: Petroleum Engineer, June 1954, vol. 26,Number 6, pages D3334.

Perry: Chemical Engineers Handbook, 1950, 3rd ed., pp. ass-901.

Sachanen: Chemical Constituents of Petroleum," Reinhold Pub. Co., 1945,page 219.

1. A PROCESS FOR REMOVING PHENYLETHANOLAMINE FROM A HYDROCARBON LIQUIDSTREAM OBTAINED IN THE SELECTIVE SOLVENT EXTRACTION OF CATALYTICREFORMATE WITH PHENYLETHANOLAMINE, SAID STREAM CONTAINING FROM ABOUT0.001 TO ABOUT 5% PHENYLETHANOLAMINE, COMPRISING THE STEPS OFINTRODUCING SAID LIQUID HYDROCARBON STREAM INTO A CLOSED VESSELCONTAINING A BED OF ADSORBENT MATERIAL, CONTACTING SAID HYDROCARBONSTREAM WITH SAID BED AT A TEMPERATURE UNDER 250*F., AND RECOVERING THEHYDROCARBON STREAM SUBSTANTIALLY FREE FROM SAID PHENYLETHANOLAMINE FROMSAID VESSEL.